THE ABDOMEN. 13 



The abdomen consists of six segments, in the queens 

 and workers, that is to say in the females, and seven in 

 the males. In the Formicidae the first segment, as a 

 general rule, forms a sort of peduncle (known as the scale 

 or knot) between the metathorax and the remainder of 

 the abdomen. In th^. Myrmicidse two segments are 

 thus detached from the rest. 



The Poneridae form, as regards the peduncle, and 

 in some other respects, an intermediate group between 

 the FormicidsB and the Myrmicida?. The second abdo- 

 minal segment is contracted posteriorly, but not so 

 much so as to form a distinct knot. 



The form of the knot ofiers in many cases valuable 

 specific characters 



I am disposed to correlate the existence of a 

 second knot among the Myrmicidse with their power 

 of stinging, which is wanting in the Formicidte. 

 Though the principal mobility of the abdomen is 

 given in the former, as in the latter, by the joint 

 between the metathorax and the knot, still the second 

 segment of the peduncle must increase the flexibility, 

 which would seem to be a special advantage to those 

 species which have a sting. 



It has indeed been said that (Ecophylla has a sting, 

 while it has only a single knot. Forel, however, has 

 shown that the sting of CEcophylla is really rudimen- 

 tary. It affords, therefore, no argument against my 

 suggestion. 



